聚驱后优势渗流通道分布特征及封堵方法

Study on Distribution and Plugging Method of Dominant Seepage Channels after Polymer Flooding

大庆油田葡I组油层大部分已进入后续水驱阶段,累计采出程度57%左右,仍有40%以上的地质储量留存地下。聚驱后葡I组油层优势渗流通道普遍发育,低效无效循环严重。综合应用取心资料、测井资料及注采动态变化资料,识别出优势渗流通道纵向上主要发育在葡I2、葡I3单元底部,平面上主要发育在河道砂体内部,且大部分平行于古水流方向。优势渗流通道厚度占10.6%,剩余储量占7.8%,吸水比例高达60.2%。为有效封堵聚驱后优势渗流通道、控制低效无效循环,自主研发具有较高弹性及强度的PPG颗粒。室内流动实验表明,PPG颗粒具有较好的抗剪切性能,可以进入油层深部封堵优势渗流通道。驱油实验表明,PPG/弱碱三元复合体系聚驱后提高采收率可达15.6%,较弱碱三元驱提高3.3%,节约聚合物用量28%。该研究成果可为油田的持续高效开发提供强力技术支撑。

Most of PI formation reservoir in Daqing Oilfield has entered the subsequent water flooding stage,the cumulative recovery rate is about 57%,and more than 40%of geological reserves are still reserved in underground.After polymer flooding,the dominant seepage channels of PI formation reservoir appeared generally,but the inefficient circulation exist and get more serious.Based on coring,well logging and injection-production dynamic changing data,it is found that the dominant seepage channels are mainly formed at the bottom of the PI2 and PI3 units vertically,as well as interior of channel sandbodies on the plane parallelling to the paleocurrent direction.The thickness of the dominant seepage channel accounts for 10.6%,the remaining reserves 7.8%,and the water absorption proportion as high as 60.2%.In order to effectively block the dominant seepage channel after polymer flooding and decrease the inefficient circulation,PPG particles with high elasticity and strength were developed.The results of indoor flow experiments show that PPG particles have superior shear resistance performance and can flow into the deep reservoir to block the dominant seepage channel.The oil displacement experiments indicate that the enhanced oil recovery of PPG/weak base ASP flooding system can reach 15.6%,which is 3.3%higher than that of weak base ASP flooding,saving 28%of polymer consumption.The results in provide strong technical support for the continuous and efficient development of oilfield.